Roundtail Paradise Fish Care
Macropodus ocellatus
The roundtail paradise fish is an East Asian labyrinth fish that can experience seasonal cold in the wild. In an aquarium it needs an appropriate cool temperature, a covered surface and space with shelter. The specialist care source recommends a footprint of 80 by 30 centimetres for a pair. Males may become territorial during reproduction. This guide distinguishes aquarium recommendations from broader ecological measurements and explains setup, feeding, behaviour and breeding. Keep access to the surface open for air breathing, and avoid treating the species as an ordinary warm-water community fish. Plan for its lower temperature and the aquarium footprint before acquiring fish. Check the condition of new arrivals and observe them carefully after introduction.
Plan your aquarium →At a glance
- Temperature
- 10–22 °C
- pH
- 6.0–7.5
- GH
- 5–20 °dGH
- Aquarium length
- At least 80 cm
- Minimum aquarium volume
- At least 72 L
- Adult size
- Up to 8 cm
- Group size
- At least 2 individuals
- Temperament
- Territorial
About this species
Macropodus ocellatus, the roundtail paradise fish, belongs to Osphronemidae. Its labyrinth organ helps it use atmospheric air, so access to the surface matters. It occurs in parts of China, Korea and Japan. The rounded caudal fin helps distinguish it from other paradise fishes. FishBase also discusses the older name Macropodus chinensis in its taxonomic context; use the currently accepted name when identifying the species.
Natural habitat
The species has been collected from ditches, rice paddies, pools, marshes, streams and quiet river backwaters. Water can become very cold in winter in parts of its range, and surfaces may freeze. This does not mean sudden aquarium temperature swings are safe. Keep conditions stable and base husbandry on the species-specific aquarium guidance.
Aquarium and layout
Seriously Fish recommends a minimum footprint of 80 × 30 cm, around 72 litres, for a pair. Use wood, branches, plants or other aquarium-safe structure to create shade and visual barriers. Floating plants can support bubble-nest building, while enough surface must remain accessible for breathing. A well-fitting lid helps prevent escapes and maintains warm, humid air above the water. A larger aquarium is needed for groups or multiple territories.
Water conditions
For aquarium care, Seriously Fish gives 10–22 °C, pH 6.0–7.5 and hardness 5–20 dGH. FishBase describes a broader ecological range, including 4–25 °C; that is not a species-specific aquarium target. This guide therefore uses the specialist aquarium values. Acclimate fish gradually and avoid rapid changes. The species is suited to cool water and should not automatically be placed in a warm tropical community aquarium.
Behaviour and group size
A pair is a cautious starting point. The species may be kept as a group in a sufficiently spacious, well-decorated aquarium, but males become territorial when breeding. Provide cover and visual barriers, and watch for persistent chasing, damaged fins or blocked access to food and shelter. Do not choose tankmates by water values alone: adult size, behaviour, temperature needs and available room also matter. No unverified tankmate combinations are listed here.
Feeding
Natural prey likely includes insect larvae. Seriously Fish recommends small live or frozen foods such as Daphnia, Artemia, white worms and grindal worms. Some fish may accept high-quality dried foods. Offer small portions suited to the mouth and remove leftovers. A varied diet is preferable to relying on a single food type; also check that the fish actually eats what is offered.
Breeding
The roundtail paradise fish builds a bubble nest at the surface. Floating vegetation can support the nest. Seriously Fish recommends a tightly fitting cover because fry need access to warm, humid air while the labyrinth organ develops. Newly free-swimming fry need very fine infusoria-grade food, followed by small live foods. Remove adults once fry swim freely if predation or disturbance is likely. Breeding requires preparation and close observation.
Sources & review
This care guide draws on several specialist sources and was last checked on .